Sunday, February 26, 2012

The first phylogenetic network (1755)

Recently, I was asked by Jesper Jansson "where exactly did the first
published phylogenetic network appear?" Obviously, the answer to this
question can depend on precisely how one defines "phylogenetic",
especially as our current understanding of the word did not arise until the
late 1800s, notably with the works of St George Jackson Mivart and Ernst
Heinrich Haeckel (who actually coined the word "phylogeny"). Nevertheless,
if we treat the concept broadly as requiring only an explicit reference to a
genealogy, then it seems possible to nominate a candidate.

Mark Ragan suggested to me that,
based on his own research as presented in his Biology Direct paper, the most likely
candidate is the genealogical network of races of dogs ("Table de L'Ordre
des Chiens") produced by Georges-Louis Leclerc, comte de Buffon
(1707-1788). I have followed up this lead, and I agree with Mark that it is
"not only a network but an explicitly genealogical one". Thus, it
seems to me that this publication certainly qualifies as a phylogenetic
network. Indeed, even Charles Darwin (from the 4th edition of the Origin,
1866, onwards) acknowledged Buffon as "the first author who in modern
times has treated it [evolution] in a scientific spirit".

Buffon's magnum opus was the 36 volumes of the Histoire naturelle générale et particulière (Imprimerie Royale,
Paris). The publishing history of this work is a mess, with dozens of French
editions and numerous translations, and both official and bootleg printings.
Indeed, this was undoubtedly the most popular work on natural history in the
late 18th and early 19th centuries. The most readily available printed version
today is the one edited by Jean Piveteau in 1954, although various editions are
now available online. So, it is important to consult the first edition to
arrive at a suitable date.

The illustration shown here is a foldout located between
pages 228 and 229 of Volume 5, published in 1755 (Volume 1 had appeared in
1749). A larger GIF version [434 KB] is
available for download from my homepage and a PDF version [2.6 MB] is on the RJR Productions webpage. The image is taken
from the online (scanned) version of the first edition, located at:
http://www.buffon.cnrs.fr/. [It is perhaps worth noting that the
first edition of this volume of the Histoire was co-authored by
Louis-Jean-Marie Daubenton; but the dog genealogy is clearly Buffon's work
alone.]

The Network

On p. 225 of the Histoire, Buffon writes: "Pour donner une idée plus
nette de l’ordre des chiens, de leur dégénération dans les différens climats,
et du mélange de leurs races, je joins ici une table, ou, si l’on veut, une
espèce d’arbre généalogique, où l’on pourra voir d’un coup d’œil toutes ces
variétés : cette table est orientée comme les cartes géographiques, et l’on a
suivi, autant qu’il étoit possible, la position respective des climats. Le
Chien de Berger est la souche de l’arbre : ....." [The 1781 English
translation by William Smellie is: "To give a clear idea of the different
kinds of dogs, of their degeneration in particular climates, and of the mixture
of their races, I have subjoined a table, or genealogical tree, in which all
these varieties may be easily distinguished. This tree is drawn in the form of
a geographical chart, preserving as much as possible the position of the
different climates to which each variety naturally belongs. The shepherd’s dog
is the root of the tree ....."]

This text is then followed by a description of the main lines of
historical relationship among the dog breeds. Then, on p. 227 Buffon further
notes: "Toutes ces races, avec leurs variétés, n’ont été produites que par
l’influence du climat, jointe à la douceur de l’abri, à l’effet de la
nourriture, et au résultat d’une éducation soignée ; les autres chiens ne sont
pas de races pures, et proviennent du mélange de ces premières races : j’ai
marqué par des lignes ponctuées, la double origine de ces races métives."
[Smellie's translation: "All these races, with their varieties, have been
produced by the influence of climate, joined to the effects of shelter, food,
and education. The other dogs are not pure races, but have proceeded from
commixtures of those already described. I have marked, in the table, by dotted
lines, the double origin of these mongrels."]

Buffon's own interpretation of this diagram as a
hybridization network thus seems clear enough. If anyone can locate an earlier
diagram that can be interpreted as a phylogenetic network, then please let me know.

Update: This later post has more information about Buffon and this network.